But so was the contract in the book - and it was fun while serving other story purposes as well. And on top of that, the contract in the book was a funny way of simultaneously revealing something about hobbits, and something about how the dwarves feel about hobbits (at this point, with sarcasm).

This contract, written up by the dwarves in advance, shows that the dwarves are cautious, legalistic and modern types. And that's just not an accurate interpretation, IMO.